Atmospheric fine and coarse mode aerosols at different environments of India and the Bay of Bengal during winter-2014: Implications of a coordinated campaign

Abstract

In this paper, we present mass concentrations of particulate matter [PM_2.5, PM₁₀ size fractions and total suspended particulates (TSP)] measured simultaneously over land stations (Kullu, Patiala, Delhi, Ajmer, Agra, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Jorhat, Itanagar, Imphal, Bhubaneswar, and Kadapa), mostly distributed across the Indo-Gangetic plain (IGP) of India as well as in the marine atmosphere over Bay of Bengal (BoB) in the period from 20 January to 3 February, 2014. The main objective of this study was to quantify the continental outflow of particulates (PM_2.5, PM₁₀ and TSP) from IGP and associated regions into the BoB along with low level north-east wind flow during winter monsoon period. The present study provides a glimpse of the aerosol loading over the IGP region. During this campaign, the highest average PM_2.5 (187.8 ± 36.5 µg m^-3, range 125.6–256.2 µg m^-3), PM₁₀ (272.6 ± 102.9 µg m^-3, range 147.6–520.1 µg m^-3) and TSP (325.0 ± 71.5 µg m^-3, range 220.4–536.6 µg m^-3) mass concentrations were recorded at Varanasi, Kolkata and Lucknow over middle and lower IGP regions. The PM_2.5 (average 41.3 ± 11.9 µg m^-3; range 15.0–54.4 µg m^-3), PM₁₀ (average 53.9 ± 18.9 µg m^-3; range 30.1–82.1 µg m^-3) and TSP (average 78.8 ± 29.7 µg m^-3; range 49.1–184.5 µg m^-3) loading over BoB were found to be comparable to land stations and suggests possible continental outflow. Over the continental region, the highest PM_2.5/PM₁₀ ratio was recorded at Delhi (0.87). The PM_2.5/PM₁₀ ratio over BoB (0.77) was found to be quite high and comparable to Varanasi (0.80) and Agra (0.79)